Abstract
Total Zn and seven measures of extractable Zn in horizons of seven soil profiles declined with increasing depth of sampling within the profile. Although not invariabily found, some extractants removed more Zn from the deepest horizons of some profiles than from the horizon sampled immediately above. This distribution pattern was more pronounced for extractable than total Zn. From 27 horizon samples containing an average of 108 ppm total Zn, 2 N MgCl2, DTPA, North Carolina, Morgan, N KCl, acidic NH4Ac, and 0.01 M CaCl2 extractants solubilized an average of 4.14, 3.77, 3.37, 1.99, 1.82, 1.64, and 0.69 ppm Zn, respectively. Extractable Zn values were positively correlated with total Zn, organic matter, percentage clay, and cation-exchange capacity, but inversely related to soil pH, base saturation, and percentage sand. Zinc concentrations in corn and in oats grown on the horizon samples were best correlated with amounts extracted by 2 N MgCl2, acidic NH4Ac, and N KCl. Regressions on extractable Zn and soil pH accounted for as much as 74 and 55% of variations in Zn content of corn and oats, respectively.
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